hi

I am relitivly inexperienced with computer but my awesome friend told me how to change the logon screen using a program called Logon loader.exe
I stupidly but accidently inserted something called explorer.exe as my logon screen, something I did not notice until to late, as the preview place did not change. It told me to restart to save changes, which I did .
Now when I logon It looks like normal windows, I think i'm running an operating system called windows XP. My friend suggested I run the computer in something called safe mode with commander prompt. But this didn't work because the diference was the 4 corners had safe mode written in them.

I urgently require help, Because I have lots of work to do, I have some very expensive programs that I have lost the disk too. I also do not have an operating system disk because it came on the computer. I also have no money to spend.

Thankyou so much if you you can help.